Review on October 17, 2008Irregular periods are experienced by nearly every woman as she enters menopause, but recent research shows that a shorter time between menstrual periods could be the first sign that menopause is on its way. Irregular periods that include heavy bleeding, however, seem to indicate other factors unrelated to ovulation, the study shows.

Shortened intervals between periods - fewer than 21 days apart - were common among women between the ages of 42 and 52 years old and in the early stages of menopause, researchers found.

These irregular periods that entailed shorter menstrual cycles were generally "anovulatory," which means that although bleeding occurred, the women did not ovulate.

As women progress through the stages of menopause, their menstrual cycle tends to expand to longer than 36 days between periods, the study found, which was published in the Journal of Obstetrics & Gynecology in July 2008.

While irregular periods related to the duration of the menstrual cycle appear to be related to whether a woman is in early stages of menopause (shorter time between periods) or later stages (longer time between periods), heavy bleeding appears to be unrelated to ovulation, says the lead researcher in the study, Dr. Bradley J. Van Voorhis of the University of Iowa College of Medicine in Iowa City.

Irregular periods involving heavy bleeding were more often seen in obese women or women who had uterine fibroids, non-cancerous growths that can cause pain as well as heavy menstrual bleeding.

The study indicates that although irregular periods can involved several different factors, such menstrual cycle duration, heavy or light bleeding, more severe cramps, etc., the type of irregular period being experienced can mean drastically different things. The type of irregular period related to the time between periods is most related to menopause, especially when the time between periods get shorter, because that can help a women understand that she is on the verge of menopause.

The study included 804 women from the United States who were tracked for a three-year period of time. These women gave sporadic urine samples throughout the three-year time period to help researchers determine if they were ovulating. Their monthly menstrual patterns were also recorded on a calendar to follow whether the cycle with shortening or lengthening.

At the beginning of the research study, the women were separated into groups determined by their menstrual patterns at that time. The women who had experienced unpredictable periods for three months prior to the study were considered on the brink of menopause. If a woman had missed two periods or more were considered to be in the twilight of menopause.

As the study progressed through the three years, the researchers found that short intervals between periods were common among women in the early stages of menopause, and about 66% of those periods were anovulatory, according to the study´s findings.

Anovulation was common in women who experienced either short or long periods.

Women who had short or long periods -- fewer than four days and more than seven days of bleeding, respectively -- also commonly had anovulatory cycles.

Alternatively, women who experienced irregular periods involving heavy bleeding had relatively few anovulation cycles, which seemed to indicate that heavy bleeding is not typically associated with hormonal changes, as are the time between periods and menopause, the study found.

The researchers concluded that the study suggests that if a woman is approaching menopause and has irregular periods involving the timing of her periods - short or long intervals or a short or long duration of bleeding - anovulation is likely the cause.

Other research has suggested that menstrual cycles that expand longer than normal could be an indication of type 2 diabetes mellitus.